Piston for internal combustion engines



March 14, 1933.

o. BAUR PISTON FOR INTERNAL COMBUSTION ENGINES Filed- March 1, 1929Patented Mar. 14, 1933 UNITED STATES PATENT OFFICE oa'rm BLUE, 0FSTUTTGAB'I, ASSIGNOB '10 A CBO AKTIENGESELLBGELIT, O! KUSSHACKT-OH-BIGI,SWITZERLAND PISTON NB INTERNAL OOKBUS'I'ION ENGINES Application filedlarch 1, 1988, Serial No. 843,725, and in Germany July 1 8, 1828.

The present invention relates to internal combustion engines of the tyin which the compression chambers comprises partly the piston so thatthat portion of the core used on casting which has to occupy this spaceis very weak and can only be removed with difficulty after casting. Theresult is that the grains of sand left behind on removing the corebecome loose on running of the engine and drop into the lubricating oilfed to the crank casing and contaminate such oil.

ill

- half.

These disadvantages are overcome according to the invention by means ofa guard shell which may be in the form of a sleeve, preferably stampedout of sheet metal, and also cast in position, which encloses the castshell and contacts with it at its cast-in edge, but leaves a spacebetween this and the side wall of the cast shell. The guard shelltherefore acts to a certain extent as a casting core for the narrowortion between the cast shell and the ad- Jacent cast wall.

The invention is more particularly described with reference to theaccompanying drawing which shows two suitable forms of construction andin which y Figure 1 is a longitudinal sectional view of one form withthe auxiliary chamber mounted in the piston. The right hand-half of thedrawing in a longitudinal section turned through 90 relative to the lefthand Figure 2 is a longitudinal sectional view of a modified form ofconstruction.

In Figure l, a indicates a cylinder, the cylinder head and 0 an inection nozzle mounted in the head. A cast piston operating in thecylinder is indicated by d and the cylinder chamber varying on thepiston stroke by c. The latter is connected with an auxiliary chamber hprovided in the piston, by means of a frusto-conical chamber f and athrottling orifice g. The cylinder chamber 6, frustoconical chamber fand auxiliar chamber h to ether form the compression 0 amber.

he base and side walls of the chamber h are formed by an insert in theform of a metal shell'z' which is only cast into the piston at its edgeIn. The cover of the chamber h and also the walls of the frusto-conicalchamber f are formed by a metal casing member m resscd into the shell1'. The cast shell z itsel is inserted in a guard shell preferably. inthe form of a sleeve n pressed out of sheet metal which encloses theshell and only contacts with the cast-in edge thereof. A free narrowannular space 0 is left between the sleeve and the side wall of theshell 2'.

The core inserted in the casting and defining the interior of the pistonneed only extend, in the form of construction shown,-up to the dottedline 1). e

The main diflerence between the second form of construction shown inFigure 2 and the first is that the sleeve n is provided with a base gwhich is arranged at a short distance from the base of the auxiliarychamber. Thus a separate air insulating chamber is formed round theportion of the edge of the outer wall of the chamber which is not castin. Further the base g prevents oil coming into contact with the base ofthe chamber, which is heated" during running, and vapourizing there toform carbon deposit.

A small hole 1' is provided in the centre of the base g of the sleevethrough which the variations in pressure set up in the air insulatingchamber, as a result of the temperature difi'erences obtaining oncasting and running, can be equalized. A depression 8 is also pressedout in the base 9 which acts as a bottom for the core used on casting.

The application of the invention is of course not limited to engines inwhich the auxiliary chamber his provided in the piston or in which theauxiliary chamber is connected with the actual cylinder chamber by athrottling member and a frusto-conical chamber. The auxiliary chambercan also '2 l morass be provided in a cast shell arranged in thecylinder head or in the cylinder.

What is claimed is:

1. A piston of an internal combustion engine comprising cylindrical sideWalls, a perforated end wall adapted to form one bounding surface of thecylinder chamber of the internal combustion engine, a shell cast at itsedges only in the perforated end Wall of said piston to form a pocketwith said perforation and a guard shell cast at its edges only with theedges of said first mentioned shell in said perforated end wall of saidBiston and an extension of said guard s ell adapted to closely followthe inner surface of said cylindrical wall 'of said piston.

2. A piston for an internal combustion engine comprising a cast pistonhavin an orifice in that face which forms a boun ing surface for theengine compression chamber, a shell cast within said piston at its edgesonly in that wall of the piston having said orifice and about saidorifice to form an auxiliary chamber leading to said compression chamberthrough said orifice, a cast in guard sleeve for the inner wall of saidpiston, said sleeve contacting with said shell at one end only andextending from the points of said I contact to closely follow'the innersurface of the cylindrical wall of the piston and to leave a spacebetween said sleeve and said shell, said sleeve having a transverselyextending end portion enclosing saidspace.

In testimony whereof I have hereunto affixed my signature. 1

' OTTMAR BAUR.

